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authorCorrado Zoccolo <czoccolo@gmail.com>2009-10-05 08:49:23 +0200
committerJens Axboe <jens.axboe@oracle.com>2009-10-05 11:03:55 +0200
commit48e025e63ac908ed6ec5394a294f4ecd510a7476 (patch)
tree49828c00687c810627f00430dd56ce9901537fc9
parent30996f40bffe73f05abb92a4cec254befa8cecf7 (diff)
downloadop-kernel-dev-48e025e63ac908ed6ec5394a294f4ecd510a7476.zip
op-kernel-dev-48e025e63ac908ed6ec5394a294f4ecd510a7476.tar.gz
cfq-iosched: fix possible problem with jiffies wraparound
The RR service tree is indexed by a key that is relative to current jiffies. This can cause problems on jiffies wraparound. The patch fixes it using time_before comparison, and changing the add_front path to use a relative number, too. Signed-off-by: Corrado Zoccolo <czoccolo@gmail.com> Signed-off-by: Jens Axboe <jens.axboe@oracle.com>
-rw-r--r--block/cfq-iosched.c9
1 files changed, 6 insertions, 3 deletions
diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c
index e7f9e4e..ae14cba 100644
--- a/block/cfq-iosched.c
+++ b/block/cfq-iosched.c
@@ -512,8 +512,11 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
rb_key = cfq_slice_offset(cfqd, cfqq) + jiffies;
rb_key += cfqq->slice_resid;
cfqq->slice_resid = 0;
- } else
- rb_key = 0;
+ } else {
+ rb_key = -HZ;
+ __cfqq = cfq_rb_first(&cfqd->service_tree);
+ rb_key += __cfqq ? __cfqq->rb_key : jiffies;
+ }
if (!RB_EMPTY_NODE(&cfqq->rb_node)) {
/*
@@ -547,7 +550,7 @@ static void cfq_service_tree_add(struct cfq_data *cfqd, struct cfq_queue *cfqq,
n = &(*p)->rb_left;
else if (cfq_class_idle(cfqq) > cfq_class_idle(__cfqq))
n = &(*p)->rb_right;
- else if (rb_key < __cfqq->rb_key)
+ else if (time_before(rb_key, __cfqq->rb_key))
n = &(*p)->rb_left;
else
n = &(*p)->rb_right;
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